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Meiosis

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Meiosis. Chapter 11-4. Chromosomes. In each cell, there is a distinct number of chromosomes ... Mitosis vs. Meiosis. Mitosis- production of two genetically ... – PowerPoint PPT presentation

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Title: Meiosis


1
Meiosis
  • Chapter 11-4

2
Chromosomes
  • In each cell, there is a distinct number of
    chromosomes
  • Example Fruit fly (Drosophila) has 8 chromosomes

3
Chromosomes
  • Half the number of chromosomes come from one
    parent (mother) and half come from the other
    parent (father)
  • Example Drosophila- 8 chromosomes
  • 4 from Mama Drosophila
  • 4 from Daddy Drosophila

4
Chromosomes
  • When half the chromosomes come from each parent,
    the sets of chromosomes are said to be homologous
  • Homologous- each chromosome from one parent has a
    corresponding chromosome from the other parent
  • Figure 11-4

5
Diploid Cells
  • Diploid- two sets a cell that contains both
    sets of homologous chromosomes (one from mom, one
    from dad)
  • Number of chromosomes is represented by the
    symbol 2N
  • Example Drosophila- 2N8

6
Haploid Cells
  • Haploid- one set cells that contain only one
    set of chromosomes
  • Gametes- sex cells haploid cells with one set
    of chromosomes
  • Number of chromosomes is represented by N
  • Example Drosophila gametes- N4

7
Meiosis
  • Meiosis- process in which the number of
    chromosomes per cell is cut in half through the
    separation of homologous chromosomes in a diploid
    cell
  • Figure 11-15 on pages 276 277

8
Meiosis
  • One diploid cells divides into four haploid cells
  • Two divisions Meiosis I Meiosis II

9
Meiosis
10
Meiosis I
  • Chromosomes combine with their homologous
    chromosome to make a tetrad
  • Tetrad- made of 2 homologous chromosomes (4
    sister chromatids)

11
Prophase I
  • In Prophase I, chomatids in the tetrad exchange
    information with other chromatids in a process
    called crossing over

12
Prophase I
  • Each chromosome pairs with its corresponding
    homologous chromosome to form a tetrad

13
Metaphase I
  • Spindle fibers attach to the chromosomes

14
Anaphase I
  • The fibers pull the homologous chromosomes apart
    to the opposite ends of the cell

15
Telophase I
  • New nuclear membranes form

16
Cytokinesis
  • Cytoplasm splits
  • Two daughter cells are formed

17
Meiosis II
  • The daughter cells from Meiosis I now undergo
    another division
  • Chromosomes in each cell consist of 2 sister
    chromatids
  • Follows steps very similar to mitosis

18
Meiosis II
19
Prophase II
  • Two daughter cells with half the number of
    chromosomes as the original

20
Metaphase II
  • The chromosomes line up in a similar way to
    mitotic metaphase

21
Anaphase II
  • The sister chromatids separate and move toward
    opposite ends of the cell

22
Telophase II Cytokinesis
  • Nuclear envelopes reform
  • Both cells divide
  • Result four haploid daughter cells

23
Mitosis vs. Meiosis
  • Mitosis- production of two genetically identical
    diploid cells
  • Meiosis- production of four genetically different
    haploid cells

24
Mitosis vs. Meiosis
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